4 Wheel Drive v. All-Wheel Drive
As we approach the midway part of winter, the groundhog says that spring is around the corner, though it is a little bit hard to believe with all the snow we have. If you have the pleasure of commuting and slipping and sliding your way down Route 22 or Interstate 684, or the Saw Mill Parkway, let’s talk about the difference between 4-wheel drive and an all wheel drive vehicle.
Let’s talk about 4WD first. With 4 WD, all the wheels are spinning at the same time being powered from a transfer case gearbox, meaning all the wheels are turning at the same time and with the same torque. The driver decides if the roads are slippery and if extra traction is needed and then engages the 4WD manually by either pushing a button or by pulling a lever. Four-wheel high is used for most types of slippery driving conditions. Four- wheel low is used for extra traction at low speeds like deep snow or mud, or for slow speed heavier pulling.
AWD is computer controlled by your vehicles on-board monitoring system. When the monitoring system senses any traction loss, the vehicle’s monitoring system will switch from 2WD to AWD. The power is then split evenly between the front and rear axles. Another difference between 4WD and AWD is that AWD wheels turn independently of one another, which is better on hard or dry surfaces.
Comparing 4WD to AWD – If you drive in snow or slippery weather having either a 4WD or AWD definitely gives you an edge over driving a front or rear wheel drive vehicle. AWD has its advantages especially driving in more urban areas. AWD also takes away any guess work about when to engage it because it is always monitoring the drive train for traction loss. In 4WD, the amount of torque being set to the wheels stays at a constant ratio. With AWD, the vehicles monitoring system will send most of the torque to the wheel with the most traction. Sometimes only one wheel will be receiving all of the traction.
Which type is better? I own both types of vehicles. I have a Saturn VUE SUV which
is AWD, and a Chevrolet Colorado pickup, which is 4WD with electronic traction control.
The traction-control systems utilize the same wheel-speed sensors employed by the antilock braking system. These sensors measure differences in rotational speed to determine if the wheels that are receiving power have lost traction. When the traction-control system determines that one wheel is spinning more quickly than the others, it automatically “pumps” the brake to that wheel to reduce its speed and lessen wheel slip. In most cases, individual wheel braking is enough to control wheel slip. However, some traction-control systems also reduce engine power to the slipping wheels. On a few of these vehicles drivers may sense pulsations of the gas pedal when the system is reducing engine power much like a brake pedal pulsates when the antilock braking system is working. Many people mistakenly believe that traction control will prevent their vehicle from getting stuck in the snow. This couldn’t be further from the truth. Traction control does not have the ability to increase traction; it just attempts to prevent a vehicle’s wheels from spinning.
While both are good in slippery conditions, I personally prefer the 4WD with the equal torque to all 4 wheels. I find it tracks better in the snow and has better traction where the AWD also does well. However, I find with the change of torque to the different axles it seems to slips more. If you are driving in off-road conditions or towing heavier equipment, the 4WD definitely is better because you can control the torque by using 4-wheel low to control the torque to all four wheels.
How many of you have had the experience of seeing a driver of either a 4WD or AWD pass you at a high rate of speed in slippery conditions only to see that driver spun out or stuck later down the road? Remember, having AWD or 4WD helps you with starting out and maintaining traction, but not in stopping and high speed turning. Always stay at a speed that keeps you in control and remember it is always important to think about stopping. Leave yourself plenty of room between yourself and the vehicle in front of you. Four-wheel drive or AWD does not give you any driving super powers or help you stop if you are driving too fast in bad conditions. Leave yourself extra travel time in bad weather. It is better to be a little late and arrive safely.
Enjoy the snow, and, Happy Motoring!